1. Field of the Invention
The present invention pertains to an LCOS display panel, and more particularly, to a single-panel type LCOS display panel which utilizes a plurality of micro dichroic filters to implement both the mirror reflection and color separation functions.
2. Description of the Prior Art
LCOS (liquid crystal on silicon) display technology is the key to reflective LCD projectors and rear-projection televisions. The LCOS displays have the advantages of tiny size, high resolution, low power, low cost, etc. The difference between an LCOS display and a TFT-LCD is that the TFT-LCD uses a glass substrate or a quartz substrate as the back plane and is provided with a light source from the back side, while the LCOS display uses a silicon substrate as the back plane and is provided with a light source from the front side. As a result, the manufacturing of LCOS display panels can be integrated into standard semiconductor processes, and therefore has high stability and resolution.
Please refer to FIG. 1, which is a schematic diagram of a conventional LCOS display panel 10. As shown in FIG. 1, the LCOS display panel 10 includes a back plane 12, a plurality of pixel electrodes arranged in an array and positioned on the surface of the back plane 12, a front plane 16 positioned in parallel and above the back plane 12, a liquid crystal layer 18 interposed between the back plane 12 and the front plane 16, and a transparent electrode layer 20 positioned on the surface of the front plane 16 facing the back plane 12. In addition, the LCOS display panel 10 further includes a top alignment layer on the surface of the transparent electrode layer 20, and a bottom alignment layer 24 positioned on the surface of the pixel electrodes 14 for controlling the arrangement direction of the liquid crystal molecules in the liquid crystal layer 18. The back plane 12 is a silicon substrate, and includes a plurality of MOS elements for respectively driving each pixel electrode 14. The front plane 16 is a transparent substrate, such as a glass substrate or a quartz substrate. The pixel electrodes 14 are made of conductive materials, such as aluminum, and must have a mirror surface for reflective lights.
A LCOS display substantially includes an optical engine and an LCOS display panel, and LCOS displays can be classified into three-panel type LCOS displays and single-panel type LCOS displays. The optical engine used in the three-panel type LCOS display must be incorporated with color separation and color combination functions so as to divide the light source into a red light beam, a green light beam, and a blue light beam, project different light beams to three different LCOS display panels, and combine different light beams reflecting from different LCOS display panels to form a colorful image. Consequently, the three-panel type LCOS display has a large size and is more expensive.
On the other hand, the single-panel type LCOS display becomes more popular since only one single panel is used. The single-panel type LCOS display is classified into color wheel type LCOS display and color filter type LCOS display. The color wheel type LCOS display utilizes a color wheel system to separate a while light source into a red light beam, a green light beam, and a blue light beam, and projects different light beams to the LCOS display panel sequentially in a short period of time. By taking account of the vision persistence characteristic of human eyes, the viewer therefore sees a color image. The color filter type LCOS display includes a plurality of color filters positioned on the front plane, as an LCD display does, so as to form a color projection image. However, both the color wheel type LCOS display and the color filter type LCOS display have some disadvantages. The color wheel type display requires the color wheel system to perform the color separation function, and thus increases the cost and difficulties in designing. As to the color filter type LCOS display, the color filters positioned in the front plane must be precisely aligned with the pixel electrodes positioned in the back plane, which is not easily done. In addition, the color filters separate the light source by absorbing the undesired light beams, and the accumulated heat cannot be dissipated via the front plane. This is another problem to be solved for the color filter type LCOS display. Furthermore, since the pixel electrodes must have a mirror surface to reflect light beams, the process complexity is increased.